In the context of the invention, "card" means all cards incorporating a hybrid or monolithic integrated circuit or "chip". They are, for example, cards in the "credit card" format still called "memory cards". The microcircuit of the card usually comprises a microprocessor or a microcontroller including memory circuits, for example of the "PROM" type. This type of card is designed to be inserted into special devices for reading and/or writing data. For simplicity, these devices are called "readers" hereinafter, although they can naturally write data and assure other ancillary functions (electrical power supply, testing, etc.). The data is generally stored in the aforementioned memory circuits in encrypted form. It is therefore read from memory locations or written to memory locations.
In all cases there are input-output members consisting of contact areas flush with the surface of one of the main faces of the card. Various standards define the position of these contact areas. They are used not only for the aforementioned data inputs-outputs but also for supplying electrical power to the microcircuit and for carrying out various checks, depending on the application concerned (presence test, etc.). The reader includes brush contacts that make galvanic contact with the aforementioned areas when the card is correctly inserted into a connector provided for this purpose.
In this application, a number of problems have to be solved simultaneously, including:
1. The microcircuit of the card must be powered up only if the brush contacts are correctly positioned on the contact areas of the card. Powering up when incorrectly positioned not only prevents operation of the reader system but can damage the electronic circuits of the microcircuit. PA1 2. In particular, the brushes for the data signals must be in position before the power supply voltage is applied to the microcircuit. PA1 3. The user may withdraw the card during processing (this is known as "pull-out"). It is then necessary for the reader to react very quickly to cut off the power supply before the brushes reach prohibited positions (i.e., positions that are hazardous to the integrity of the circuits of the microcircuit). PA1 4. The use of any non-standard object, for example an electrically conductive plate or a faked card, whether by accident or in the case of attempted fraud, can also cause faults. PA1 a connector including a body supporting brush contact members designed to come into electrical contact with conductive areas associated with said microcircuit of said card when the latter is inserted into the connector; and PA1 an integrated circuit including means for monitoring inserting the card into the card reader and withdrawing it therefrom, said circuit being connected, on the one hand, to at least some of said brush contact members and, on the other hand, to this electronic circuit of the card reader.
In all these cases it is necessary to disable the reader and to interrupt the electrical power supply to limit the risk of damage to the circuits and/or of attempted fraud.
There are many reader systems aimed at reducing some or all of these problems. They can be classified into three major categories.
The first category comprises electronic detector systems.
In systems of this type, before applying an electrical voltage to the microcircuit, an electrical test is carried out, for example by measuring the resistance between the brush contacts. If these tests do not yield expected values within a given range, the card has been inserted incorrectly or a foreign body has been inserted in its place.
This type of system has various drawbacks,
In these systems, the card is positioned against an abutment before it comes into contact with the brushes. Contact is made by relative displacement of the card towards the brushes perpendicularly to the surface of the card (main faces).
Security can be assured only by correct operation of the mechanical parts of the system. However, the latter can be backed up by an "end of travel" contact which disables the power up sequence if the card is not in the correct position. A power up sequence can be established by the height of the brushes or by initializing the electronics on the closing of a "card present" contact. A system of this kind is described in EP 0 139 593, for example. The above patent describes a smart card reader apparatus comprising:
The main disadvantage of this system is the fact that the mechanical arrangements required to implement the aforementioned functions are complex and costly.
The third category comprises systems with brush contacts and an "end of travel" contact. A system of this kind is disclosed in FR-A-2 623 314, for example.
In these systems, the connectors into which the cards are inserted are provided with an "end of travel" contact which initiates the powering up of the microcircuit when the card is in the correct position.
The mechanical arrangements are simple and of low cost but have the disadvantage of requiring the incorporation into the reader electronics of control circuits associated with the aforementioned "end of travel" contact.
Additionally, there are drawbacks common to more than one system.
In the case of electronic detector systems and systems using "end of travel" contacts, functions associated with the position of the card have to be implemented in the electronics of the reader, and therefore allowed for in the design of each application.
For reasons of speed of development and reduction of costs, reader apparatus designers usually employ microprocessor-based systems. These naturally have good flexibility since it is sufficient to modify the program if the characteristics of a given application change for any reason. However, it is well known that programmed logic is slower then hardwired logic executing the same functions.